JPH11311981A - Liquid crystal display device drive method, liquid crystal display device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control display luminance of a non-display area, to display required gradation and to cancel an incongruous sense as a whole equipment by providing a period controlling the display gradation of the non-display area to be made a non-display state. SOLUTION: For controlling the display gradation of an unselected area, a voltage level regularly used in an X driver 4 is used in a Y driver 5, and the gradation of the unselected area is realized. In the period A, voltage application for a display area is performed. A selection level is applied successively to a scan electrode Y arranged on the display area, and an unselected level is applied to other unselected scan electrodes, and a voltage controlling a display state of a pixel answering to a scanning line selected according to that is applied successively to a signal electrode X. On the other hand, the period B is the period for the non-display area. The period for controlling the display gradation of the non-display area is provided in a scan period, and a method eliminating the necessity changing a drive voltage by fixing a duty is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a liquid crystal display device, a liquid crystal display device, and an electronic apparatus, and more particularly, to a liquid crystal display device having a partial display function.

[0002]

2. Description of the Related Art The number of display dots of a display device used in a portable electronic device such as a mobile phone has been increasing year by year so that more information can be displayed, and accordingly, the power consumption of the display device has also increased. Are coming. Since the power source of the portable electronic device is a battery, the display device is strongly required to have lower power consumption so that the battery life is prolonged. Therefore, in a display device having a large number of display dots,
When necessary, the entire screen (the entire displayable area) is displayed, but in standby mode, only a part of the display panel is displayed as the minimum necessary display, and other areas are not displayed, and power consumption is reduced. A method for reducing this is being studied.

Many conventional liquid crystal display devices have a function of controlling display / non-display of the entire screen, but have a function of setting only a certain area of the screen to a display state and setting other areas to a non-display state. For example, Japanese Patent Application Laid-Open No. 6-95621 and Example 1 and Japanese Patent Application Laid-Open No. 7-281632 have been proposed. Further, the present inventors have proposed a display device that divides the entire screen into regions and performs display / non-display as Japanese Patent Application No. 9-518751.

FIG. 6 and FIG.
A configuration example of the signal will be described below. FIG. 6 is a block diagram of a liquid crystal display device having this configuration example. A block 601 is a liquid crystal display panel in which a substrate on which a plurality of scanning electrodes are formed and a substrate on which a plurality of signal electrodes are formed are opposed to each other at intervals of several μm, and liquid crystal is sealed between the intervals. This detailed configuration is shown later in FIG. Block 602 includes:
Block 603 is a Y driver for driving the scanning electrodes.
Is an X driver for driving the signal electrodes. Block 60
Reference numeral 4 denotes a power supply, which generates voltages of 5V and 24V. A plurality of voltage levels required for driving the liquid crystal are formed by a driving voltage forming circuit in block 605, and are applied to the liquid crystal display panel via an X driver and a Y driver. Block 608 is a scanning control circuit for controlling the number of scanning electrodes to be scanned.
A block 606 is, for example, a controller in the main body of the personal computer, and generates data and timing signals required for display. A circuit that receives a signal from the controller 606 and forms a timing signal, a display data signal, and a control signal necessary for circuits such as the X driver 603 and the Y driver 602 is a drive signal control circuit of the block 607.

FIG. 7 shows a general configuration of these liquid crystal display panels. 7A and 7B show a configuration of a so-called simple matrix panel, wherein FIG. 7A is a plan view and FIG. 7B is a cross-sectional view. 1
001 is an upper polarizer, 1002 is a first substrate such as glass, which has optical transparency, and a signal electrode 1003 is provided on the first substrate, and the signal electrode 1003 is provided on a second substrate 1007.
A scanning electrode 1005 is provided so as to intersect with.
In order to hold the liquid crystal 1004 between the two substrates, a sealant 1006 is provided. 1008 is a lower polarizing plate. The above is the configuration of the transmission type. In the case of the reflection type, the configuration is such that the reflection plate is provided below the lower polarizing plate 1008. 320 signal electrodes are X1 to X320, and scanning electrodes are Y1 to Y320.
The description will be made with an example of 400 pieces of 400 pieces.

In the above configuration, a selection voltage is sequentially applied to the scanning electrodes Y row by row, and a non-selection voltage is applied to the other rows. A signal voltage corresponding to ON / OFF of each pixel in the selected row is applied to the signal electrode X for each row.

In this conventional example, the partial display is the left half screen, that is, the case where only the first display screen D1 and the second display screen D2 are displayed, and the upper half thereof, that is, the first display screen D1, is displayed.
Is described in which only the display screen D1 is displayed.

To display D1 and D2, data of the entire screen is transferred to a built-in data register of the X driver 603 for driving the non-display area, and the X driver 6 for the display area is transferred.
By transferring the display data only to the shift register 03 and outputting it to the signal electrodes, the screen operation of the areas D1 and D2 in the entire display screen is performed. In this conventional example, the power consumption for this data transfer is reduced by halving the data transfer to the X driver 603.

Next, a case where only D1 is displayed will be described. The number of scanning electrodes Y is, for example, 400. The whole screen is displayed by sequentially selecting all the scanning electrodes Y,
To display only the upper half, the upper half
Only the 00 lines (Y1 to Y200) are sequentially selected, and the lower half 200 lines (Y201 to Y400) are not selected. When 400 lines are selected, the display duty is 1/400, and when 200 lines are selected, the display duty is 1/200. Therefore, it is necessary to change the setting of the drive voltage. In the case of 1/400 duty, assuming that a drive voltage range of 28 V is required, 1/20 to maintain the same contrast.
In the case of 0 duty, it is necessary to adjust to 20V. This adjustment is performed inside the drive voltage control circuit 805.

[0010]

In the above-mentioned prior arts proposed so far, the control of the display luminance is described in detail for the display area of the entire screen, but the control of the non-display area is not described. It is supposed to be a choice. For this reason, depending on the design of the device incorporating the liquid crystal display device, even if it is desired to have a black background or a gray level instead of a white background, it cannot be controlled in the conventional example, and the device user (user) cannot control the device. There was an uncontrollable problem in the desired background.

For example, as shown in FIG. 5, in a display mode of a liquid crystal, an applied voltage is a threshold voltage (threshold voltage).
In a region lower than Vth, there is a normally black mode liquid crystal having a low transmittance (reflectance in a reflection type). When this liquid crystal is used, in a conventional example in which no applied voltage is applied to a non-display area, a black background is obtained, which may be strange when viewed as a whole electronic device. In addition, even when a normally white mode liquid crystal is used, there is a problem that the luminance of the non-display area cannot be adjusted.

[0012]

According to the present invention, there is provided a liquid crystal display having a displayable area formed based on a plurality of signal lines and scanning lines crossing each other. A method of driving a liquid crystal display device comprising a panel, and having a function of setting only a part of the displayable area to a display state and setting another area to a non-display state, the display floor of the non-display area to be set to the non-display state A key control period (B) is provided.

By providing this period B, it is possible to control the display gradation in the non-display area, and at the same time,
With non-display area and full screen (whole displayable area)
There is no need to change the drive voltage when displaying
The power supply configuration can be simplified.

Further, in the driving method of the liquid crystal display device according to the present invention, the voltage level applied to the signal line for controlling the display gradation of the non-display area is changed to a signal line driver for applying a voltage to the signal line. It is characterized by a voltage level to be applied. For this reason, it is not necessary to set a new voltage level for display control of the non-display area, so that the power supply configuration can be simplified, and an increase in cost and power consumption can be prevented.

Further, the driving method of the liquid crystal display device according to the present invention is characterized in that the driving method of the liquid crystal display panel is a multi-line selection driving method for simultaneously selecting a plurality of scanning lines. For this reason, it is possible to cope with a liquid crystal having a high-speed response.

Further, a liquid crystal display device of the present invention uses the above-described method for driving a liquid crystal display device, and an electronic apparatus of the present invention has the liquid crystal display device mounted thereon. Since it is possible to control the gradation of the non-display area of the liquid crystal display device, there is an advantage that the non-display area of the entire display device and the entire device can perform display without a sense of incongruity.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing one embodiment of a liquid crystal display device according to the present invention.

Block 1 is a liquid crystal display panel, and the detailed configuration is the same simple matrix type panel as that of the conventional example shown in FIG. Block 2 is a controller for generating data and timing signals necessary for display, Block 3 is a power supply for supplying a power supply voltage necessary for driving the liquid crystal display panel, and Block 4 is a signal electrode (signal line) corresponding to display data. A signal line driver (X driver) for applying a selected voltage, a block 5 is a scanning line driver (Y driver) for applying a selection voltage or a non-selection voltage to a scanning electrode (scanning line), and a block 6 receives a voltage from the power supply 3. 5 shows a drive voltage generation circuit that forms and outputs a plurality of voltage levels required by each driver of the liquid crystal display panel. Since the basic elements are the same as those described in the related art, a detailed description of each element will be omitted, and necessary matters regarding the driving waveform which is an important point of the present invention will be described.

FIG. 2 shows a case where the displayable area (full screen) of the liquid crystal display panel is divided into a display area and a non-display area (A
To D). According to the present invention, non-display areas such as A, B, C, and D can be set. As described in the related art, these non-display state setting methods include the non-display area 2 in which the display area is divided by the X driver 4 and the Y display area.
The driver 5 can classify the display area into the non-display area 1 which is divided.

Here, in the case of the non-display area 1, the display brightness adjustment of the non-display area can be realized by controlling the signal electrodes X arranged in the non-display area collectively. This means that the display gradation control of the non-display area can be performed only by transferring the display data to the shift register of the X driver 4 by one pixel. That is, when a selection voltage is applied to the scanning electrode, the voltage waveform output from the X driver 4 to the signal electrode X is the same as the voltage waveform for each signal electrode arranged in the non-display area 1. The region where the region is formed by the matrix of the scanning electrode and its signal electrode is
It becomes a non-display area. Since this waveform itself does not have any difference from the conventional waveform, a detailed description is omitted.

Next, the case of the non-display area 2 will be described.
In this case, the output from the Y driver 5 to the scanning electrode Y in the non-display area becomes a non-selection voltage in the related art, so that the voltage applied to the pixels in the non-selection area 2 cannot be controlled. However, in the present invention, in order to control the display gradation of the non-selected area 2, the voltage level normally used by the X driver 4 is used by the Y driver 5 to control the gradation of the non-selected area 2. To achieve.

This will be described in detail with reference to a voltage waveform diagram.

FIG. 3 is a voltage waveform diagram for explaining the present invention. (A) is a voltage waveform for driving a scanning electrode (for example, the Y1 electrode in FIG. 7) arranged in the display area D1, and (b) is a signal electrode (for example, X1 in FIG. 7) arranged in the display area D1. (C) is a voltage waveform for driving a scanning electrode (for example, the Y400 electrode in FIG. 7) disposed in a non-display area, and (d) is a voltage waveform for driving a scanning electrode (for example, the Y400 electrode in FIG. 7). (For example, X1 and Y1 in FIG. 7)
FIG. 4 is a waveform diagram of a voltage applied to a pixel at the intersection of 400).

The voltage waveform diagram of FIG. 3 shows the voltage waveform during two frames (two vertical scans). In (a),
As for the voltage level, VH is the selection level (selection voltage) of the scanning electrode Y, VL is the selection level (selection voltage) of the scanning electrode Y for inverting and selecting the potential to prevent liquid crystal burn-in, and VC is the scanning. This is a voltage level (non-selection voltage) for setting the electrode Y to a non-selection state. In (b), V2,
-V2 is a voltage level of the signal electrode X for controlling on / off of the display state of the selected pixel. In the frame period 1, the level is -V2 when on, and V2 level when off. Is to select.

In the period A, a voltage is applied for the display area. Here, the waveform is the same as that of the conventional voltage application. That is, the selection levels (VH, VL) as shown in FIG. 3A are sequentially applied to the scanning electrodes Y arranged in the display area, and the non-selection level V is applied to other non-selected scanning electrodes.
C, and the voltage for controlling the display state of the pixel corresponding to the scanning line selected in response to the voltage C is changed to a voltage during the period A in FIG.
As described above, the voltage is sequentially applied to the signal electrodes X for each scanning electrode. In this period A, the scanning electrodes in the non-display area are
As shown in FIG. 3C, the voltage VC of the non-selection level is kept applied, and the voltage applied to the pixels in the non-display area is also shown in FIG.
As shown in (d), according to the display data of the display area, V2 and-
V2.

On the other hand, the period B is a period for a non-display area. In the prior art, in order to change the duty, the drive voltage is changed without this period. However, in the present invention, a method is used in which a period for gradation control of a non-display area is provided within a scanning period and the duty is not changed, so that it is not necessary to change the drive voltage. Although this period B is superfluous, it is a period in which there is no problem even if the operation of the liquid crystal display device is stopped. Therefore, by stopping the operation in this period, power consumption does not increase.

The period B is further divided into a period C and a period D. In the period C, the voltage level -V2 is selected as the applied voltage of the scan electrode Y in the non-selected area (see FIG. 3C). On the other hand, as shown in FIG.
The voltage is fixed at two levels. Therefore, the voltage applied to the pixels in the non-display area can be V2-(-V2), that is, a voltage twice as high as the V2 level (see FIG. 3D). Conversely, in the period D, the voltage level V2 is selected as the voltage applied to the scan electrode Y in the non-selected area (see FIG. 3C). On the other hand, as shown in FIG.
Since the voltage is fixed at two levels, the voltage applied to the pixels in the non-display area is VC, that is, 0 V (FIG. 3).
(D)). In this way, the non-display area can selectively display the same display state as on or off, or an intermediate gray level, according to the time width of the voltage application period of 2 × V2 in period C.

As described above, the display gradation of the non-display area 2 can be freely controlled by changing the temporal ratio between the period C and the period D. Since the switching between the period C and the period D occurs only once during one frame period, an increase in power consumption is minimized. That is, when voltage switching occurs, current consumption increases in a driver or the like, but low power consumption can be maintained unless voltage switching is provided frequently during a scanning period.

For example, the total number of scanning electrodes is 200,
It is assumed that the display is the upper 40 lines and the non-display is 160 lines. At this time, the total number of selection periods (periods during which a selection voltage is to be applied to the scan electrodes in the displayable area) is 200 from 200 scan electrodes in total. Forty of these periods are used in the display area as period A, and the remaining 160 periods are period B. At this time, in order for the pixels in the non-display area 2 to apply the same voltage as during the display period, the period C is 97 periods and the period D is the remaining 63 periods. Find more. Similarly, the off-state voltage is 40 periods in the period C and 120 periods in the period D.

That is, by changing the period C from the period 40 to the period 97, it is possible to select 57 gradations of the display luminance level of the pixels in the non-display area 2.

In this embodiment, a driving method of inverting the polarity of the voltage applied to the liquid crystal of the pixel in the frame periods 1 and 2 is employed.

[Second Embodiment] In the above description, as the driving method, a method of selecting the scanning electrodes line by line has been described. Recently, a multi-line driving method has been developed in which two or more scanning electrodes are selectively driven at the same time due to an increase in response speed of liquid crystal. This multi-line driving method can drive a liquid crystal with a high response speed. The present invention is also applicable to this driving method.

This embodiment is different from the first embodiment in that
The driving method is a multi-line driving method, and the other basic configuration of the liquid crystal display panel is the same as that of the first liquid crystal display panel described above.
Since the third embodiment is the same as the first embodiment, a detailed description is omitted.
That is, the basic block configuration of the liquid crystal display device is the same as that of FIG. 1, and the configuration of the liquid crystal display panel is the same as that of FIG. However, the detailed configuration in the block of FIG. 1 is different from that of the first embodiment because of the multi-line driving method.

FIG. 4 is a voltage waveform diagram when four scanning electrodes are driven in the multi-line driving method according to the present embodiment. The voltage waveform diagram of FIG. 4 shows the voltage waveform in one frame (one vertical scan) period. (A) is a voltage waveform for driving a scanning electrode (for example, the Y1 electrode in FIG. 7) arranged in the display area D1. In order to make the drawings easy to see, the same four are selected, but one of them is shown as a representative. In the multi-line driving method for simultaneously selecting four scanning electrodes, four simultaneous selections are performed within one frame period, and VH is applied to three scanning electrodes when the four scanning electrodes are simultaneously selected. VL is applied to one scanning electrode, and VL is applied to each scanning electrode once in one frame period. (B) is a voltage waveform for driving a signal electrode (for example, the X1 electrode in FIG. 7) arranged in the display area D1. (C) is a voltage waveform for driving a scanning electrode (for example, the Y400 electrode in FIG. 7) arranged in the non-display area, and (d) is a pixel in the non-display area (for example, X1 and Y in FIG. 7).
FIG. 4 is a waveform diagram of a voltage applied to a pixel at the intersection of 400).

In FIG. 4A, the voltage level is V
H and VL are the selection level (selection voltage) of the scanning electrode Y, VC
Is a non-selection level (non-selection voltage) for bringing the scanning electrode Y into a non-selection state. Because of multi-line drive, V
The potential difference between H and VL with respect to VC is 比 べ compared to the case where one line is selected as shown in FIG. In (b), V2 and -V2 are levels of the signal electrode X for controlling on / off of the display state of the selected pixel.
When four lines are selected simultaneously, two levels (V
3, -V3) is required to apply a potential to the signal electrode X, and it is necessary to select a potential from four potential levels. However, to simplify the description, the signal electrode from two potential levels is required. It is omitted from the drawing where the potential is selected.

In the case of the multi-line driving method, one scanning electrode is selected four times in one frame. A voltage waveform diagram in a case where the selection is evenly distributed (periodically selected within one frame period) is shown. A period A for displaying the display area in accordance with the display data and a period B for controlling the gray scale of the non-display area are provided for each of the four equal dispersions. The gradation control period B of the non-display area is further divided into a period C and a period D, and a voltage is applied to the liquid crystal of the pixel in the period C, and the voltage is not applied to the liquid crystal of the pixel in the period D. It is.

In the period A, a voltage is applied for the display area. Here, the waveform becomes similar to that of the conventional voltage application. That is, a selection level (VH, VL) as shown in FIG. 4A is applied to the four scanning electrodes Y arranged in the display area, and the four scanning electrodes Y are sequentially and simultaneously selected for every four scanning electrodes. A non-selection level VC is applied to other non-selected scan electrodes. A voltage for controlling the display state of the pixel corresponding to the selected scanning line is sequentially applied to the signal electrode X for each selection period, as shown in period A of FIG. In this period A, the non-selection level voltage VC is still applied to the scan electrodes Y in the non-display area as shown in FIG. 4C, and the voltage applied to the pixels in the non-display area is also shown in FIG. It changes according to the display data of the display area as in d).

On the other hand, the period B is a period for a non-display area. In the prior art, in order to change the duty, the drive voltage is changed without this period. However, in the present invention, a method is used in which a period for gradation control of a non-display area is provided within a scanning period and the duty is not changed, so that it is not necessary to change the drive voltage. Although this period B is superfluous, it is a period in which there is no problem even if the operation of the liquid crystal display device is stopped. Therefore, by stopping the operation in this period, power consumption does not increase.

The period B is further divided into a period C and a period D. In the period C, the voltage level -V2 is selected as the voltage applied to the scanning electrode Y in the non-selected area (see FIG. 4C). On the other hand, as shown in FIG.
The voltage is fixed at two levels. Therefore, the voltage applied to the pixels in the non-display area can be V2-(-V2), that is, a voltage twice as high as the V2 level (see FIG. 4D). Conversely, in the period D, the voltage level V2 is selected as the voltage applied to the scanning electrode Y in the non-selected area (see FIG. 4C). On the other hand, as shown in FIG.
Since the voltage is fixed at two levels, the voltage applied to the pixels in the non-display area is VC, that is, 0 V (FIG. 4).
(D)). In this way, the non-display area can selectively display the same display state as on or off, or an intermediate gray level, according to the time width of the voltage application period of 2 × V2 in period C. In the multi-line driving, since the potential level of the signal electrode X is more than two levels, the gray level of the non-display area can be controlled by selecting the potential level to be applied to the signal electrode in the period B. it can.

As described above, the display gradation of the non-display area 2 can be freely controlled by changing the temporal ratio between the period C and the period D. The switching between the period C and the period D does not occur many times during the frame period (four times in the case of multi-line driving of simultaneous selection of four lines), so that an increase in power consumption is minimized. That is, when voltage switching occurs, current consumption increases in a driver or the like, but low power consumption can be maintained unless voltage switching is provided frequently during a scanning period.

Although the present embodiment has been described on the basis of multi-line driving in which four lines are simultaneously selected, the number of simultaneously selected scanning electrodes is not limited to this.

[Electronic Equipment According to Modifications and the Present Invention] The order in which the period D exists after the period C has been described above.
The invention is not limited to this, and the period C may come after the period D. Further, although the description has been made in the order of the period B after the period A, the present invention is not limited to this, and the period A may come after the period B.

When the liquid crystal display device according to the above embodiment is mounted as a display unit of an electronic device, a selectively provided non-display area on a display screen of the electronic device can be displayed with a desired gradation. It is clear that the discomfort of the entire device can be eliminated.

[0045]

As described above, according to the present invention, in a liquid crystal display device which divides a screen into a display region and a non-display region and controls the display, it is possible to control the display luminance of the non-display region. Can display a desired gradation of an electronic device equipped with the device, so that it is possible to eliminate an uncomfortable feeling as a whole device.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a liquid crystal display device of the present invention.

FIG. 2 is a diagram illustrating a display area and a non-display area.

FIG. 3 is a voltage waveform diagram when selecting one line at a time.

FIG. 4 is a voltage waveform diagram when four lines are selected at a time.

FIG. 5 is a diagram showing a voltage-transmittance relationship for describing a mode of a liquid crystal.

FIG. 6 is a block diagram of a conventional liquid crystal display device.

FIG. 7 is a structural view of a liquid crystal display panel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel 2 ... LCD controller 3 ... Power supply 4 ... X driver 5 ... Y driver 6 ... Drive voltage generation circuit

Claims (5)

[Claims] 1. A liquid crystal display panel having a displayable area formed based on a plurality of signal lines and scanning lines crossing each other, wherein only a part of the displayable area is in a display state and other areas are not displayed. A method for driving a liquid crystal display device having a function of setting a display state, wherein a period for controlling a display gradation of a non-display area to be set to the non-display state is provided. 2. The voltage level applied to the signal line for controlling a display gradation of the non-display area according to claim 1, wherein the voltage level applied to the signal line is a voltage level applied to a signal line driver applying voltage to the signal line. A method for driving a liquid crystal display device. 3. The driving method for a liquid crystal display device according to claim 1, wherein the driving method of the liquid crystal display panel is a multi-line selection driving method for simultaneously selecting a plurality of scanning lines. 4. A liquid crystal display device using the method for driving a liquid crystal display device according to claim 1. 5. An electronic device equipped with the liquid crystal display device according to claim 4.